Intriguing ‘Effect’ explores science of human feelings

British playwright Lucy Prebble has achieved the rare feat, in her 2012 four-hander “The Effect,” of writing a play that is both funny and devastating.

San Francisco Playhouse’s production, with its excellent cast and its sensitive direction by Bill English, captures every nuance in this layered and unpredictable tale of a scientific experiment gone disastrously awry.

Psychology student Connie (a captivating Ayelet Firstenberg) and Tristan (a rich portrayal by the always excellent Joe Estlack) are making a few bucks by signing up as guinea pigs in a closely observed clinical trial of a new super anti-depressant (neither subject presents as depressed) and are sequestered for several weeks during the length of the trial run.

By coincidence, they share the same birthday.

And by coincidence — or perhaps as the effect of increasing dosages of the experimental “agent” (or is one of them on a placebo?) — there’s a mutual attraction, and things spin dangerously out of control.

Just for starters, the research is compromised.

Meanwhile, the interaction between the psychiatrist who’s been hired to monitor the proceedings, Lorna (Susi Damilano, showing the full range of her acting talent), and Toby, the psychiatrist heading up the study (the equally wonderful Robert Parsons), seems awkward and tense.

Is that because they have opposing viewpoints about the efficacy of psych meds? Lorna believes that they simply don’t work, at least not in the long run, and that science will eventually scoff at this “chemical imbalance stuff” that’s the theory du jour.

It’s Toby’s position, though, that “Emotions aren’t really real”; it’s all about readjusting the brain.

As their heated arguments veer into the personal realm, it becomes evident that there’s a lot at stake for both psychiatrists.

And there’s just as much at stake for Tristan and Connie.

Prebble’s inquiry into the issues and ethics involved with experimenting on human beings is focused and sharp; there are issues, as it turns out, not just for the test subjects but also for the researchers.

Only a few times is Prebble tonally off-key, most notably in a sort of surreal stream-of-consciousness monologue by Lorna that’s extraneous. But the speech is balanced out by any number of outstanding scenes, including, in particular, two between Connie and Tristan: one charming and comical, another that makes you ache for both characters.

Nina Ball’s spare and sterile set, and Theodore J.H. Hulsker’s digital-data projections, create a perfect context for this beautifully realized, provocative play.

The Effect
Presented by San Francisco Playhouse
Where: 450 Post St., S.F.
When: 7 p.m. Tuesdays-Thursdays, 8 p.m. Fridays, 3 and 8 p.m. Saturdays, 2 p.m. Sundays; closes April 28
Tickets: $20 to $125
Contact: (415) 677-9596,

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